A photosensitive resin composition may be applied on a substrate to form a paint film and used to form a pattern by subjecting a specific portion of the paint film to exposure by light irradiation using a photomask and the like and then subjecting a non-exposure portion to a development treatment to remove the non-exposure portion. This photosensitive resin composition has been used for a photocurable ink, a photosensitive printing plate, various photoresists, a color filter photoresist for a LCD, a photoresist for a resin black matrix, a transparent photosensitive material or the like since the photosensitive resin composition may be polymerized and cured by light irradiation.
The photosensitive resin composition usually includes an alkali soluble resin, a polymerizable compound including an ethylenically unsaturated bond, a photopolymerization initiator and a solvent.
In the photosensitive resin composition, an alkali soluble resin allows the photosensitive resin composition to have adhesive strength with a substrate and thus a coating may be formed, is dissolved in an alkali liquid developer to allow a fine pattern to be formed, and simultaneously serves to prevent an obtained pattern from being broken during a post-treatment process by imparting strength to the pattern. Further, the alkali soluble resin has great effects even on heat resistance and chemical resistance.
In general, the photosensitive resin composition is formed as a coating film having a thickness of 3 μm or more and most of the coating film needs to be developed, and thus the photosensitive resin composition needs to be dissolved in a large amount in a liquid developer within a short time period. In addition, when development is not clearly performed, various display defects such as direct spots due to residues and alignment defects of liquid crystals may occur. Therefore, the photosensitive resin composition needs to have excellent developability. Moreover, when a photosensitive resin composition is applied on a glass substrate with a large surface area, it is difficult for the substrate to be subjected to full-surface exposure, and thus the substrate is subjected to exposure in multiple sequences. Thus, when the photosensitive resin composition has low sensitivity, the time needed for the exposure process becomes longer, resulting in a drop in productivity, and thus high sensitivity is required.
Moreover, even in a high temperature process at 200° C. or higher, excellent thermal stability for maintaining the shape and thickness, high compress strength sufficient to resist against external pressure and excellent chemical resistance are required. In addition, excellent stability with time may stably exhibit characteristics which are constantly required without any changes even under long-term storage conditions, and thus excellent stability with time is required. However, a photosensitive resin composition that meets all the standards in terms of heat resistance, chemical resistance, developability, sensitivity and stability with time has not been yet developed.
Furthermore, in a process of using the above-described photosensitive resin composition, in order to improve a yield per unit time of the process, exposure time and development time are reduced. Thus, there is a need for improving sensitivity and developability, compared to photosensitive resin compositions that are known in the art.
A method of using a photoactive compounds with high sensitivity or increasing the amount of the photoactive compound has been used to increase sensitivity of a photosensitive resin composition. However, the photoactive compounds with high sensitivity has a relatively expensive problem. In addition, when the amount of the photoactive compound is increased, a lot of sublimate foreign bodies occurred in the process of post baking may contaminate the oven or contaminate the components such as liquid crystal in the LCD panel.
Recently, a method of photocrosslinking an alkali-soluble resin and an ethylenically unsaturated compound has been made in an effort to introduce a photopolymerizable functional group to a side chain of an alkali-soluble resin used in a photosensitive resin composition.
However, even though photosensitivity and a ratio of the photopolymerizable reactive group introduced into the alkali-soluble resin are in a positive relationship, since the photopolymerizable reactive group is introduced into an acid group portion of the alkali-soluble resin, if the ratio of the photopolymerizable reactive group in the alkali-soluble resin is increased, the ratio of the remaining acid group is relatively reduced to reduce developability.
Meanwhile, a contact angle of a known photosensitive resin composition is controlled by a kind and an amount of surfactant. However, there are many cases where the contact angle is not controlled by the surfactant due to a limitation of raw material of the photosensitive resin composition. This is because the surfactant is partially removed during a manufacturing process of a color filter.
Accordingly, there is a demand for developing the photosensitive resin composition increasing the contact angle while the surfactant is not removed during the manufacturing process of the color filter in the art.